Qt4: fix memleak when album arts.

(cherry picked from commit d4c7ef27)
Signed-off-by: Rémi Duraffort <ivoire@videolan.org>

modules/gui/qt4/input_manager.cpp

@@ -641,7 +641,10 @@ const QString InputManager::decodeArtURL( input_item_t *p_item )
     /* Taglib seems to define a attachment://, It won't work yet */
     url = url.replace( "attachment://", "" );
 #endif
-    return qfu( psz_art ? psz_art : "" );
+
+    QString path = qfu( psz_art ? psz_art : "" );
+    free( psz_art );
+    return path;
 }
 
 void InputManager::UpdateArt()